Electron discharge device having filamentary cathode tensioning means



Dec. 14, 1965 M. E. WEISS 3,223,877

ELECTRON DISCHARGE DEVICE HAVING FILAMENTARY CATHODE TENSIONING MEANS Filed July 25 1949 INVENTOR. Mori'tmePE. Weiss United States Patent ELECTRON DISCHAR GE DEVICE HAVING FILA- MENTARY CATHODE TENSIONING MEANS Mortimer E. Weiss, Flushing, N.Y., assiguor, by mesne assignments, to Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Filed July 25, 1949, Ser. No. 106,722 4 Claims. (Cl. 313-278) The present invention relates to electron discharge devices and more particularly, to an improved tensioning device for filamentary cathodes of such devices.

An object of the present invention is the provision of a novel means for applying tension to a filamentary cathode of an electron discharge device.

Another object of the present invention is the adaptation of a torsion spring to filamentary cathode tensioning devices.

A further object of the present invention is the provision of a filament tensioning device in which there is no increase in tension applied to the filament when the electron discharge device is subjected to extremely high accelerations, particularly to accelerations in the direction along the axis of the tube.

Still a further object of the present invention is the provision of a filament tensioning device which has relatively no degrees of freedom in planes either longitudinal or transverse to the tube axis as compared with presently known filament tensioning devices, whereby no increase in tension is applied to the filament under high acceleration.

In presently known systems of which I am aware, in which the filament tensioning device has a comparatively long spring arm crossing the top bridge or spacer of an electron discharge tube, high accelerations in directions longitudinal of the axis of the tube and applied toward the base of the tube cause a substantial increase in the tension applied to the filament. This increase in tension is equal to the product of the weight of the top filament tab and the spring by the acceleration. At accelerations of the order of many thousand times the acceleration of gravity, the increase in tension added to that normally exerted by the tensioning device may easily exceed the ultimate tensile strength of the filament wire. Also, in previously known arrangements of which I am aware, lateral accelerations acting on the spring tension arm, can also add to the tension applied to the filament by a factor equal to the product of the weight of the top filament tab and the spring by the lateral acceleration. Since the present filament tensioning device has substantially no freedom of movement in directions either longitudinal or transverse to the axis of the tube, there is substantially no increase in tension applied to the filament for high accelerations in either direction.

The foregoing objects and others which may appear from the following detailed description are attained in accordance with one aspect of the present invention by providing a torsion spring arrangement for applying tension to the filament. The spring arrangement is arranged to act substantially wholely in torsion, and is directly connected to the end of this filament without the intermediary of a long lever arm. A hereinafter described embodiment of the present invention includes a transverse rod supported above the top mica of the vacuum tube substantially directly over the filament hole in the mica. A light torsion coil spring is mounted about the transverse rod and has one end welded to the rod. Over the torsion coil spring is provided a sleeve which is welded to the spring at the other end. The top filament tab is then welded to the sleeve after the sleeve is rotated to Patented Dec. 14, 1965 "ice an extent sufiicient to apply a pre-determined tension to the filament.

The present invention will be more fully understood by reference to the following detailed description which is accompanied by a drawing in which FIG. 1 illustrates in a longitudinal, partly sectional View; an electron discharge tube implying principles of the present invention; FIG. 2 is a fragmentary perspective view of a portion of the tube shown in FIG. 1, illustrating in more detail an application of the principles of the present invention; FIG. 3 is an exploded perspective view of the tensioning arrangement of FIG. 2; and FIG. 4 is a view similar to FIG. 2 but illustrating a modified form of the invention.

Referring now to FIG. 1, there is shown an evacuated casing 10 which may be made of vitreous material, such as glass, and having a number of connection leads 12 passing through a header or base 13. Casing 10 may be metal, if desired. (A mount structure 14, within the evacuted casing 10, includes a pair of insulating spacer members 16 and 18 preferably of mica. The spacer members may be so arranged as to be at least in part supported in position by the sidewalls of the envelope 10. Along substantially the longitudinal axis of the envelope 10 is provided a filamentary cathode 20 passing through holes in spacers 16 and 18, one of which is indicated generally at 22 in FIG. 2. The holes may, if desired, be triangular so that one corner positively locates this filament while still permitting ready assembly of the mount. The triangular apertures are preferably so arranged that one apex of each triangle lies on the longitudinal axis of the tube. Surrounding the filamentary cathode 20 are a number of control electrodes or grids 24 and 26 and an anode 28. Each of the grids are provided with side rods 30 which extend through apertures in the spacers 16 and 18 and thus serve to maintain the grids in their proper position relative to one another and to the filament. As shown more clearly in FIG. 2, the anode 28 may be in two sections, each section being supported by side rods which also pass through the mica spacers. The anode may of course be a single piece of metal formed in a hollow box or hollow cylindrical shape. Also, instead of using side rods for securing the anode to the mica spacers, tabs, integral with the anode member and pressing the mica spacers, may be used. One of the side rods of each anode section is extended upwardly to form a bridge 31 whereby the two sections of the anode are connected in parallel.

An additional pair of support rods 32 and 33 pass through apertures in spacer members 16 and 18 and are secured rigidly in position. Rods 32 and 33 are extended above the top spacer 16 a sufficlent distance to provide room for mounting the filament tensioning arrangement thereon. The filament tensioning arrangement includes a transverse rod 34 welded or otherwise secured at each end to the supor t rods 32 and 33, a helical coil spring 36 and an outer sleeve member 38. The filament tensionmg arrangement is assembled by first welding spring 36 at one end to the transverse rod 34 and thereafter weldmg sleeve 38 to the opposite end of spring 36. Rod 34 is then welded to the support rods 32 and 33. The weld of sleeve 38 to spring 36 is made with a very light pressure, for example, by using welding tweezers to avoid making a second weld of the spring to the rod 34. In continuing the assembly of the tube, the filament 20, provided with an end tab 21 at each end, is inserted through holes 22 and the bottom tab 21 welded to one of the lead-in conductors 12. Sleeve 38 is then turned in a direction to store a predetermined amount of ten- S1011 in spring 36. That is, it is, in the view shown in FIG. 1, turned counterclockwise a predetermined number of turns and then the top filaments tab 21 is welded with light pressure to sleeve 38. The torsion spring 36,

in attempting to unwind then applies a predetermined tension to the filament 20.

From an inspection of FIGS. 1 and 2 it will be seen that the resulting filament tensioning arrangement has practically no freedom of movement either longitudinally of rod 34 or transversely thereto. The tab 21, being short and light, has substantially no lever arm action, which would provide increased tension on the spring 20 during high accelerations.

I have discovered that under some circumstances, it is unnecessary to employ the tensioning sleeve 38 but that the filament tab 21 may be directly welded to a point on the torsion spring 36. This form of construction is shown in FIG. 4. Since the same reference numerals are applied to FIG. 4 as to the figures showing the previously d scribed embodiment, it is believed unnecessary to describe FIG. 4 in further detail. Its operation will be apparent from the mode of operation of the embodiments shown in FIGS. 1, 2 and 3.

While I have shown and particularly described several embodiments of the present invention, it should be clearly understood that my invention is not limited thereto, but that modifications may be made.

What is claimed is:

1. An electron discharge tube having a filamentary cathode, a support for one end of said cathode, and a tensioning means connected to the other end of said cathode, said tensioning means including a support, a helical spring, and a sleeve surrounding said spring, said other end of said cathode being directly connected to said sleeve.

2. An electron discharge tube having a filamentary cathode, said cathode having connector tabs at each end, a support for one end of said cathode connected to the tab at said one end, and a tensioning means connected to the other end of said cathode, said tensioning means including a support, a helical spring and a sleeve surrounding said spring, the connector tab at the other end of said cathode being directly connected to said sleeve.

3. An electron discharge tube having a mount structure including upper and lower insulating spacers, central apertures in said spacers, a filament passing through said apertures, one end of said filament being secured to a support adjacent one of said spacers, the other end of said filament being secured to a tensioning means on the other of said spacers, said tensioning means including a bar passing over the aperture on said other spacer, a helical spring secured on one end to said bar, and a sleeve surrounding said spring and secured to the other end of said spring, said filament being secured to said sleeve substantially directly over the aperture in said other spacer.

4. An electron discharge tube having, within an evacuated casing, a mount structure including upper and lower insulating spacers, central apertures in said spacers, a filamentary cathode passing through said apertures, an anode and a number of control electrodes surrounding said filamentary cathode, one end of said filamentary cathode being secured to a support adjacent the lower one of said spacers, the other end of said filamentary cathode being secured to a tensioning means on the other of said spacers, said tensioning means including a number of support rods passing through said spacers, a horizontal bar connected across saisd suport rods and passing substantially over the aperture in the upper of said spacers, a helical spring secured at one end to said bar, and a sleeve over said spring and secured to the other end of said spring, said filamentary cathode being secured to said sleeve substantially directly over the aperture in said upper spacer.

References Cited by the Examiner UNITED STATES PATENTS 1,566,293 12/1925 Van Der Biji 313262 2,402,797 6/ 1946 Wood 313-27 8 2,412,800 12/1946 Curtis 313-278 2,476,940 7/1949 Wood 3l3-69 FOREIGN PATENTS 401,740 11/1933 Great Britain.

JOHN W. HUCKERT, Primary Examiner.

RALPH G. NILSON, JAMES L. BREWRINK,

WILLIAM G. WILES, Examiners. 

1. AN ELECTRON DISCHARGE TUBE HAVING A FILAMENTARY CATHODE, A SUPPORT FOR ONE END OF SAID CATHODE, AND A TENSIONING MEANS CONNECTED TO THE OTHER END OF SAID CATHODE, SAID TENSIONING MEANS INCLUDING A SUPPORT, A HELICAL SPRING, AND A SLEEVE SURROUNDING SAID SPRING, SAID OTHER END OF SAID CATHODE BEING DIRECTLY CONNECTED TO SAID SLEEVE. 